The Bureau
of Economic Geology (BEG) and Pemex Exploración y Producción
(Pemex) conducted a study of the Miocene chronostratigraphy, structure,
geochemistry, and plays in the Burgos Basin and adjacent south Texas within
an area of approximately 32,500 km2, onshore and offshore (to 500 isobath).
Using more than 15,000 linear km of 2-D seismic lines, 98 onshore wells,
2 offshore wells, and paleontological data, we defined plays by age (upper
upper Miocene, lower upper Miocene, middle Miocene, and lower Miocene)
and paleogeography (shelf, slope, and basin floor). These play types were
inferred from depositional geometry and the amplitude character and geometry
of reflectors. Sets of parallel reflectors present updip (westward) of
shelf-edge clinoforms characterize the shelf play, subdivided into an
expanded-shelf play in a zone of major growth faults. The slope play consists
of clinoforms and subtle stratal downlaps. The internal architecture of
this seismic facies is complex, with downlapping strata indicating locally
developed lowstand prograding complexes. The basin floor play comprises
parallel sets of reflectors downdip (eastward) of the slope clinoform
play. A fourth play type was defined from onlap of strata onto diapirs
in the eastern salt province. Areas where intervals are not present due
to diapir piercement were also mapped to provide a framework for mapping
the onlap plays.

This
play framework provides the means for initial exploration of Miocene strata
and evaluation of key play elements (reservoir presence and quality, seal,
trap, source, and migration) in this structurally complex, underexplored
basin. The relative importance of these play elements varies systematically
for each play, especially between the onshore shelf plays and the offshore
deep-water plays, where fault complexity and stratigraphic variability
is significantly greater.